This invention relates generally to a screwdriver for driving collated screws which are joined together in a strip, and, more particularly, to a power screwdriver with a slide body which extends and retracts in driving collated screws and which can be maintained in a retracted position.
Collated screwstrips are known in which the screws are connected to each other by a holding strip of plastic material. Such strips are taught, for example, by U.S. Pat. No. 4,167,229 issued Sep. 11, 1979 and its related Canadian Patents 1,040,600 and 1,054,982 as well as U.S. Pat. No. 4,930,630, the disclosures of which are incorporated herein by reference. Screws carried in such screwstrips are adapted to be successively incrementally advanced to a position in alignment with and to be engaged by a bit of a reciprocating, rotating power screwdriver and screwed into a workpiece. In the course of the bit engaging the screws and driving it into a workpiece, the screw becomes detached from the plastic holding strip leaving the strip as a continuous length.
In the use of such collated screwstrips in screwdrivers, the strip serves a function of assisting in guiding the screw into a workpiece and, to accomplish this, the holding strip is retained against movement towards the workpiece. In the screwstrip, each screw to be driven has its threaded shaft threadably engaged in a threaded sleeve of the holding strip such that on the screwdriver engaging and rotating each successive screw, the screw turns within the sleeve which acts to guide the screw as it moves forwardly into threaded engagement into the workpiece. Preferably, only after the tip of the screw becomes engaged in the workpiece, does the head of the screw come into contact with the sleeves. Further, forward movement of the screw into the workpiece then draws the head downwardly to engage the sleeve and to rupture the sleeve by reason of the forward movement of the head with the strip retained against movement towards the workpiece. The sleeve preferably is configured to have fragile straps which break on the head passing through the sleeve such that the holding strip remains intact as a continuous length. Since the holding strip is a continuous length, on advancing the screwstrip with each successive screw to be driven, it necessarily results that portion of the holding strip from which each screw has been driven are also advanced to exit from the power screwdriver.
Known power screwdrivers for driving such collated screwstrips include U.S. Pat. No. 4,146,071 to Mueller et al, issued Mar. 27, 1976, and U.S. Pat. No. 5,186,085 to Monacelli, issued Feb. 16, 1993, the disclosure of which are incorporated herein by reference. Such known power screwdrivers include a rotatable and reciprocally moving screwdriver shaft which is turned in rotation by an electric motor. A screwdriving bit forms a forwardmost portion of the shaft for engaging the head of each successive screw as each screw is moved into a driving position, axially aligned under the screwdriver shaft.
Known power screwdrivers for collated screwstrips suffer the disadvantage appreciated by the applicant that they are dedicated to drive collated screws. In use, they cannot be used to drive separate screws or to withdraw misdriven screws or other screws which are desired to be removed. Known power screwdrivers for collated screwstrips also suffer the disadvantage that it is difficult to engage and change bits mounted to the front end of the drive shaft.
To at least partially overcome these disadvantages of previously known screwdrivers, the present invention provides a power screwdriver for collated screwstrips which may be latched or locked in a retracted position for use as a normal power screwdriver so as to drive separate screws and/or to withdraw screws and the like independently of the collated screwstrip.
An object of the present invention is to provide a power screwdriver adapted for driving collated screws which may be latched in an extension limiting position in which the screwdriver may be used independently of the collated screwstrip.
Another object is to provide a screwdriver for collated screws which permits latching in a position for use as a screwdriver with or without the collated screwstrip engaged in the screwdriver assembly.
Another object is to provide a screwdriver for collated screwstrips which may be latched in a position permitting access to the drive shaft and/or bit for facilitating removal and/or changing of the bit and/or to permit manual engagement with the bit of screws separate from the collated screwstrip.
Accordingly, the present invention provides a power screwdriver attachment for driving collated screws having a housing and a slide body movable between extended and retracted positions to drive screws from a collated screwstrip, a latching system to releaseably latch the slide body in an extension limiting position in which the power driver is able to be used as a power screwdriver independent of the collated screwstrip. The screwdriver attachment may be used as a power screwdriver for driving or withdrawing screws whether or not a screwstrip is engaged in the attachment. When latched, the screwdriver attachment permits the collated screwstrip to be withdrawn or inserted and, as well, permits the drive shaft to be rotated either forwardly or rearwardly. The screwdriver attachment preferably has a depth adjustment mechanism to adjust the extent to which any screw is driven into a workpiece and which mechanism remains operative when the attachment is latched in the extension limiting position. In the extension limiting position, a bit carried on a forward end of a driver shaft is preferably accessible for manual engagement of separate screws thereon to permit driving or removal of such separate screws with the power screwdriver attachment. The latching system preferably is readily manually accessible to a person using the power tool.
The construction of the screwdriver is preferably compact and lightweight. A compact design may be achieved by camming portions of the slide body extending within the housing rearwardly past the coupling of the housing to the power driver. A lightweight design utilizes lightweight synthetic plastic and nylon materials to comprise major portions of the element.
In one aspect, the present invention provides an apparatus for driving with a power driver a screwstrip comprising threaded fasteners such as screws or the like, which are joined together in a strip comprising:
a housing;
an elongate drive shaft for operative connection to a power driver for rotation thereby and defining a longitudinal axis;
a slide body coupled to the housing for displacement parallel to the axis of the drive shaft between an extended position and a retracted position;
a spring biasing said slide body forwardly relative to the housing parallel to the axis to the extended position;
screw feed advance mechanism to engage the screwstrip and successively, incrementally advance screws on the screwstrip to be axially in alignment with said drive shaft for driving of the screws by the drive shaft, and
the screw feed advance mechanism coupled between the slide body and the housing whereby displacement of the slide body relative the housing between the extended position and the retracted position activates the screw feed advance mechanism to advance successive screws;
an extension limit mechanism activatable to releasably prevent the housing and slide body from being extended relative each other towards the extended position beyond an extension limit position. The extension limit mechanism may, in one aspect, lock the housing and slide body together against relative movement. Preferably, the slide body has a guide channel mechanism for said screwstrip extending through the slide body,
a guide mechanism to locate successive of the screws advanced via the guide channel to be axially in alignment with said drive shaft for engagement in driving of the screws from the guide mechanism by the drive shaft, and
screw feed advance mechanism to engage the screwstrip and successively, incrementally advance screws on the screwstrip through the guide channel mechanism.